The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
During combustion, an internal combustion engine oxidizes gasoline and combines hydrogen (H2) and carbon (C) with air. Combustion creates chemical compounds such as carbon dioxide (CO2), water (H2O), carbon monoxide (CO), nitrogen oxides (NOx), unburned hydrocarbons (HC), sulfur oxides (SOx), and other compounds. During an initial startup period after a long soak, the engine is “cold” and may resist fuel vaporization, charge ignition and/or complete combustion of the fuel. A catalytic converter treats exhaust gases from the engine. During the startup period, the catalytic converter is also “cold” and does not operate optimally, resulting in unacceptably high emissions.
In one conventional approach, an engine controller commands a lean air/fuel (A/F) ratio and supplies a reduced mass of liquid fuel to the engine to provide compensation. More air is available relative to the mass of liquid fuel to sufficiently oxidize the CO and HC. However, the lean condition reduces fuel vaporization and combustion stability, adversely impacting vehicle drivability.
In another conventional approach, the engine controller commands a fuel-rich mixture for stable combustion and good vehicle drivability. A secondary air injection system provides an overall lean exhaust A/F ratio. The secondary air injector injects air into the exhaust stream during the initial start-up period. The additional injected air heats the catalytic converter by oxidizing the excess CO and HC. The warmed catalytic converter oxidizes CO and HC and reduces NOx to lower emissions levels. However, the secondary air injection system increases cost and complexity of the engine control system and is only used during a short initial cold start period.
In still another conventional approach, an external device such as a resistive heater and/or a bulb heater can be inserted into the engine compartment to heat the engine prior to starting. The obvious disadvantages of this approach include the cost of the additional equipment, as well as the time required to install and remove the equipment between engine start cycles, and the energy consumed by such equipment. For example, supplemental fuel systems are used in Brazil. Additional fuel rail heaters are also used to promote fuel vaporization.